Electrolytic capacitor

ABSTRACT

An electrolytic capacitor includes a capacitor element and an electrolyte solution. The capacitor element includes: an anode foil provided with a dielectric layer on the anode foil; a cathode foil disposed to face the anode foil; and a conductive polymer layer disposed between the anode foil and the cathode foil. The cathode foil is provided with a first layer disposed on the cathode foil, the first layer including at least one selected from the group consisting of carbon, nickel, a nickel compound, titanium, and a titanium compound. The conductive polymer layer includes a conductive polymer in contact with at least a part of a surface of the first layer. The surface of the first layer has projections and recesses.

RELATED APPLICATIONS

This application continuation of U.S. application Ser. No. 16/287,618,filed Feb. 27, 2019, which is a continuation of U.S. application Ser.No. 15/725,344, filed Oct. 5, 2017 (now U.S. Pat. No. 10,262,806), whichis a national stage of International Application No. PCT/JP2016/001333,filed Mar. 10, 2016, which claims the benefit of Japanese ApplicationNo. 2015-091447, filed Apr. 28, 2015, the disclosures of which areincorporated in their entirety by reference herein.

TECHNICAL FIELD

The present disclosure relates to an electrolytic capacitor including aconductive polymer layer (solid electrolyte layer) and an electrolytesolution.

BACKGROUND

As small-sized, large capacitance, and low ESR (Equivalent SeriesResistance) capacitors, promising candidates are electrolytic capacitorsincluding an anode body on which a dielectric layer is formed and aconductive polymer layer formed so as to cover at least a part of thedielectric layer.

In Unexamined Japanese Patent Publication No. 2012-174865, it isproposed, in a solid electrolytic capacitor that includes a capacitorelement having a conductive polymer layer in the capacitor element,that, for example, a carbon layer be formed on a cathode foil of thecapacitor element to suppress generation of an electrostatic capacity ina cathode. In Unexamined Japanese Patent Publication No. 2012-174865,the conductive polymer layer is formed through heat polymerization byimmersing a wound body in a polymerization liquid containing a rawmaterial of a conductive polymer, the wound body being obtained bywinding an anode foil and the cathode with a separator interposedbetween the anode foil and the cathode.

In Unexamined Japanese Patent Publication No. 2008-010657, anelectrolytic capacitor obtained by impregnating with an electrolytesolution a capacitor element is proposed. The electrolytic capacitorincludes an anode foil on which a dielectric layer is formed, a cathodefoil, a separator interposed between the anode foil and the cathodefoil, and a conductive polymer layer formed on surfaces of thedielectric layer, the separator, and the cathode foil. In UnexaminedJapanese Patent Publication No. 2008-010657, the conductive polymerlayer is formed by impregnating the anode foil, the cathode foil, andthe separator with a dispersion in which particles of a conductivepolymer are dispersed.

SUMMARY

One aspect of an electrolytic capacitor according to the presentdisclosure includes a capacitor element and an electrolyte solution. Thecapacitor element includes: an anode foil provided with a dielectriclayer on the anode foil; a cathode foil disposed to face the anode foil;and a conductive polymer layer disposed between the anode foil and thecathode foil. The cathode foil is provided with a first layer disposedon the cathode foil, the first layer including at least one selectedfrom the group consisting of carbon, nickel, a nickel compound,titanium, and a titanium compound. The conductive polymer layer includesa conductive polymer in contact with at least a part of a surface of thefirst layer. The surface of the first layer has projections andrecesses.

According to the present disclosure, it is possible to reduce the ESReven with use of an electrolyte solution and secure a high capacitance,in an electrolytic capacitor including a conductive polymer layer formedwith use of a dispersion or a solution containing a conductive polymer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic sectional view illustrating an electrolyticcapacitor according to one exemplary embodiment of the presentdisclosure.

FIG. 2 is a schematic view illustrating a configuration of a capacitorelement of the electrolytic capacitor in FIG. 1.

DESCRIPTION OF EMBODIMENTS

Prior to describing exemplary embodiments of the present disclosure,problems in a conventional electrolytic capacitor are described.

In the solid electrolytic capacitor as in Unexamined Japanese PatentPublication No. 2012-174865, a high capacitance is expected by formingan inorganic conductive layer such as a carbon layer. In addition, ESRis expected to be reduced by improving conductivity of the cathode. Onthe other hand, a property of restoring the dielectric layer isincreased with use of the electrolyte solution in Unexamined JapanesePatent Publication No. 2008-010657.

In a case of using a polymerization liquid containing a raw material ofa conductive polymer as in Unexamined Japanese Patent Publication No.2012-174865, however, even use of the electrolyte solution is unlikelyto increase the property of restoring the dielectric layer. In addition,in a case of using a dispersion or a solution containing a conductivepolymer together with an electrolyte solution, formation of an inorganicconductive layer on a cathode side as in Unexamined Japanese PatentPublication No. 2012-174865 sometimes makes insufficient adhesionbetween a conductive polymer layer and the inorganic conductive layer.The insufficient adhesion increases contact resistance between a cathodeand the conductive polymer layer so that it is difficult to reduce theESR.

The present disclosure provides an electrolytic capacitor reducing theESR even when using an electrolyte solution and having a highcapacitance. The electrolytic capacitor includes a conductive polymerlayer formed with use of a dispersion or a solution containing aconductive polymer.

Hereinafter, an exemplary embodiment of an electrolytic capacitoraccording to the present disclosure is described with appropriatereference to drawings. The exemplary embodiments below, however, is notto limit the present disclosure.

<<Electrolytic Capacitor>>

FIG. 1 is a schematic sectional view illustrating an electrolyticcapacitor obtained by a production method according to one exemplaryembodiment of the present disclosure. FIG. 2 is a schematic viewillustrating a partially developed capacitor element included in theelectrolytic capacitor.

In FIG. 1, the electrolytic capacitor includes capacitor element 10, andcapacitor element 10 is housed in an outer case (specifically, bottomedcase 11) together with an electrolyte solution (not shown). The outercase includes bottomed case 11 in which capacitor element 10 is housed,insulating sealing member 12 that seals an opening of bottomed case 11,and base plate 13 that covers sealing member 12. Bottomed case 11 is, ata part near an opening end, processed inward by drawing, and is, at theopening end, curled to swage sealing member 12.

As illustrated in FIG. 2, capacitor element 10 includes anode foil 21connected to lead tab 15A, cathode foil 22 connected to lead tab 15B,and separator 23. Anode foil 21 and cathode foil 22 are wound withseparator 23 interposed between the anode foil and the cathode foil, andsuch capacitor element 10 is also referred to as a wound body. Anoutermost periphery of capacitor element 10 is fixed with fastening tape24. FIG. 2 shows partially developed capacitor element 10 before theoutermost periphery of the capacitor element is fixed.

In capacitor element 10, anode foil 21 is a metal foil whose surface isroughened so as to have projections and recesses, and a dielectric layeris formed on the metal foil having the projections and recesses. Cathodefoil 22 opposite to anode foil 21 is a metal foil whose surface isroughened so as to have projections and recesses, and an inorganicconductive layer is formed on the metal foil having the projections andrecesses. A conductive polymer is attached to at least a part of asurface of the dielectric layer on anode foil 21 and at least a part ofa surface of the inorganic conductive layer on cathode foil 22 to form aconductive polymer layer. The attaching position of the conductivepolymer is not limited to this case, but the conductive polymer may beattached to any position between anode foil 21 and cathode foil 22. Forexample, the conductive polymer covers at least a part of the surface ofthe dielectric layer formed on anode foil 21, and may further cover atleast a part of the surface of the inorganic conductive layer on cathodefoil 22 and/or at least a part of a surface of separator 23.

As described above, the conductive polymer layer is formed between anodefoil 21 and cathode foil 22. In the electrolytic capacitor, theconductive polymer (specifically, a film including the conductivepolymer) that covers at least a part of the surfaces of, for example,the anode foil, the cathode foil, and the separator is generallyreferred to as a solid electrolyte layer (or a conductive polymer layer)in some cases.

Hereinafter, a configuration of the electrolytic capacitor according tothe exemplary embodiment of the present disclosure is described in moredetail.

A capacitor element includes an anode foil on which a dielectric layeris formed, a cathode foil having a roughed surface on which an inorganicconductive layer is formed, and a conductive polymer layer interposedbetween the anode foil and the cathode foil. The capacitor element mayalso include a separator as necessary.

(Capacitor Element)

(Anode Foil)

Examples of the anode foil include a metal foil whose surface isroughened. A type of the metal that constitutes the metal foil is notparticularly limited, but it is preferred to use a valve metal such asaluminum, tantalum, or niobium, or an alloy including a valve metal,from the viewpoint of facilitating formation of the dielectric layer.

Roughening the surface of the metal foil can be performed by a publiclyknown method. By the roughening, a plurality of projections and recessesare formed on the surface of the metal foil. The roughening ispreferably performed by subjecting the metal foil to an etchingtreatment, for example. The etching treatment may be performed by, forexample, a DC electrolytic method or an AC electrolytic method.

(Dielectric Layer)

The dielectric layer is formed on a surface of the anode foil.Specifically, the dielectric layer is formed on a roughened surface ofthe metal foil, so that the dielectric layer is formed along an innerwall surface of pores and pits on the surface of the anode foil.

A method for forming the dielectric layer is not particularly limited,and the dielectric layer can be formed by subjecting the metal foil toan anodizing treatment. The anodizing treatment may be performed by, forexample, immersing the metal foil in a anodizing solution such as anammonium adipate solution. In the anodizing treatment, a voltage may beapplied in a state in which the metal foil is immersed in the anodizingsolution, as necessary.

Normally, a large metal foil formed of, for example, a valve metal issubjected to a roughening treatment and an anodizing treatment from theviewpoint of mass productivity. In this case, the treated foil is cutinto a desired size to arrange anode foil 21 on which the dielectriclayer is formed.

(Cathode Roil)

A metal foil may be used for cathode foil 22. A type of the metal is notparticularly limited, but it is preferred to use a valve metal such asaluminum, tantalum, or niobium, or an alloy including a valve metal.

Generally, a method for producing the conductive polymer layer isclassified to two cases. One case is forming the conductive polymerlayer with use of a dispersion obtained by dispersing fine particles ofa conductive polymer in a dispersion medium or a solution obtained bydissolving a conductive polymer in a solvent. And the other case isforming the conductive polymer layer by polymerizing a precursor of aconductive polymer (e.g., a monomer or an oligomer that is to be a rawmaterial of the conductive polymer) while the precursor is in contactwith the anode foil and the cathode foil.

In the latter case, the polymerization proceeds on the surfaces of theanode foil and the cathode foil to form the conductive polymer layer, sothat a relatively strong film is formed. The film, however, is too denseto allow an electrolyte solution to spread out on the surface of theanode foil, and thus the property of restoring a damaged dielectriclayer is inferior. Further, due to strong reactivity of an oxidant for apolymerization reaction or a monomer itself, the cathode foil and theanode foil corrode to consequently deteriorate contact between the foilsand the conductive polymer layer. And thus the capacitance decreases orincreasing the ESR. An oxidant and a monomer that remain after thepolymerization are not sufficiently taken away even by washing toadversely affect a life of the electrolytic capacitor.

In the present disclosure, the conductive polymer layer is formed withuse of a dispersion obtained by dispersing fine particles of aconductive polymer in a dispersion medium, or a solution obtained bydissolving a conductive polymer in a solvent. Such a conductive polymerlayer is formed by contacting the dispersion or the solution to theanode foil and the cathode foil to cause attachment of the conductivepolymer to a periphery of the anode foil and the cathode foil. Such aconductive polymer layer is homogeneous, and has a high flexibility, andan excellent retainability of an electrolyte solution, but has lowadhesion between the conductive polymer layer and the anode foil or thecathode foil (or the inorganic conductive layer on the surface of thecathode foil). Particularly, when an electrolyte solution is used, theelectrolyte solution infiltrates between the conductive polymer layerand the inorganic conductive layer, easily hindering contact between theconductive polymer layer and the inorganic conductive layer to make itdifficult to achieve a high capacitance and reduce the ESR.

In the present disclosure, the surface of the cathode foil is roughenedand the inorganic conductive layer is formed on the roughened surface,so that the adhesion between the conductive polymer layer and theinorganic conductive layer can be increased in spite of forming theconductive polymer layer with use of the dispersion or the solution. Inspecific description, the inorganic conductive layer is formed on theroughed surface of the cathode foil to form projections and recessesalso on a surface of the inorganic conductive layer that is in contactwith the conductive polymer layer. The projections on the surface of theinorganic conductive layer form a first region where the inorganicconductive layer is in contact with the conductive polymer layer,whereas the recesses form a second region where the inorganic conductivelayer is not in contact with the conductive polymer layer. In the secondregion, a gap is formed between the inorganic conductive layer and theconductive polymer layer, so that even when an electrolyte solutioninfiltrates between the inorganic conductive layer and the conductivepolymer layer, the electrolyte solution flows into the gap. Therefore,in the first region, the electrolyte solution is prevented from enteringbetween the conductive polymer layer and the inorganic conductive layer,or an amount of the electrolyte solution between the layers decreasesthat enters or remains between the layers. As a result, it is possibleto secure a high contact pressure, suppress a decrease in adhesionbetween the conductive polymer layer and the inorganic conductive layer,and suppress an increase in resistance of an interface.

A degree of surface roughening of the cathode foil can be represented bya surface expansion rate. The surface expansion rate on the surface ofthe cathode foil ranges, for example, from 1.3 cm²/cm² to 550 cm²/cm²,inclusive, preferably from 1.5 cm²/cm² to 500 cm²/cm², inclusive,further preferably from 2 cm²/cm² to 120 cm²/cm², inclusive. With thesurface of the cathode foil having a surface expansion rate in theseranges, the first region and the second region are formed in a goodbalance to allow easy securement of high adhesion between the conductivepolymer layer and the inorganic conductive layer. Further, with thesurface of the cathode foil having a surface expansion rate in theseranges, it is easy to suppress attachment or adsorption of, for example,moisture, a byproduct, or gas to the surface of the cathode foil beforethe inorganic conductive layer is formed. As a result, a morehomogeneous inorganic conductive layer is easily formed, also from sucha viewpoint, easily suppress to decrease adhesion. With the surface ofthe cathode foil having a surface expansion rate ranging from 10 cm²/cm²to 60 cm²/cm², inclusive, it is possible to further suppress to decreaseadhesion, so that a decrease in capacitance and an increase in ESR canbe suppressed in use of the electrolytic capacitor for a long period.

Roughening the surface of the cathode foil can be performed by apublicly known method, and the roughening may be performed by etching.The etching treatment may be performed by, for example, a DCelectrolytic method or an AC electrolytic method. From the viewpoint ofeasily securing a high capacitance even when repeating charging anddischarging, the roughening is preferred to be performed by etching.

(Inorganic Conductive Layer)

The inorganic conductive layer is desired to be formed of an inorganicmaterial having conductivity and is distinguished from a conductivepolymer layer formed of an organic material.

Examples of the conductive inorganic material that forms the inorganicconductive layer include, in addition to conductive carbon, a metal anda conductive metal compound. Examples of the conductive carbon includeamorphous carbon, carbon black such as acetylene black, soft carbon,hard carbon, graphite, and a carbon fiber such as a carbon nanotube. Asthe metal and the metal compound, one that is less likely to form apassive film by, for example, contacting with air is preferred. Examplesof the metal include titanium, a titanium alloy, nickel, and a nickelalloy. Examples of the metal compound include a nitride and a carbide,and a nitride is preferable. As a metal that constitutes the metalcompound, there can be exemplified titanium and/or nickel. The inorganicconductive layer may include one of these inorganic materials or two ormore of these inorganic materials.

Although the inorganic conductive layer may include the conductiveinorganic material and a binder, a ratio of the conductive inorganicmaterial is preferred to be as high as possible. An proportion of theconductive inorganic material in the inorganic conductive layer ispreferably 95% by mass or more or 99% by mass or more, for example. Inaddition, the inorganic conductive layer may be a layer formed of theconductive inorganic material. The inorganic conductive layer may beformed by forming a layer including the conductive inorganic materialand a binder and removing the binder by a heat treatment. Especially,the inorganic conductive layer is preferred to be a deposited film ofthe conductive inorganic material (particularly, conductive carbon suchas amorphous carbon).

Even when the cathode foil and the inorganic conductive layer are formedof the same material, a distribution of a metal is different between thecathode foil and the inorganic conductive layer (for example, thedistribution of a metal is rougher in the inorganic conductive layerthan in the cathode foil), so that it is possible to distinguish thecathode foil from the inorganic conductive layer in a sectional electronmicrograph.

From the viewpoint of increasing adhesion between the inorganicconductive layer and the cathode foil, the inorganic conductive layermay further include a conductive base layer as necessary. The base layerthat constitutes a part of the inorganic conductive layer is preferredto include a conductive inorganic material such as a metal or aconductive metal compound among the conductive inorganic materialsexemplified above. As the metal, titanium is preferable, and as themetal compound, a titanium nitride is preferable.

A thickness of the inorganic conductive layer ranges, for example, from1 nm to 10 μm, inclusive. When the inorganic conductive layer is adeposited film, the thickness of the inorganic conductive layer ranges,for example, from 1 nm to 100 nm, inclusive. When the inorganicconductive layer is formed of a layer including the conductive inorganicmaterial and a binder, the thickness of the inorganic conductive layermay range, for example, from 100 nm to 10 μm, inclusive. The thicknessof the inorganic conductive layer may be an average thickness obtainedby averaging thicknesses measured at a plurality of points (e.g., 10points) in a sectional image.

The inorganic conductive layer having a thickness in the rangesdescribed above easily suppresses a decrease in adhesion between theinorganic conductive layer and the conductive polymer layer to alloweasy securement of high conductivity.

(Separator)

As separator 23, for example, a nonwoven fabric may be used thatincludes a fiber of, for example, cellulose, polyethylene terephthalate,a vinylon, or a polyamide (e.g., an aliphatic polyamide and an aromaticpolyamide such as aramid).

Capacitor element 10 can be manufactured by a publicly known method. Forexample, capacitor element 10 may be manufactured by stacking anode foil21 on which the dielectric layer is formed and cathode foil 22 on whichthe inorganic conductive layer is formed, with separator 23 interposedbetween the anode foil and the cathode foil, and then forming theconductive polymer layer between anode foil 21 and cathode foil 22.Capacitor element 10 may also be manufactured by winding anode foil 21on which the dielectric layer is formed and cathode foil 22 on which theinorganic conductive layer is formed, with separator 23 interposedbetween the anode foil and the cathode foil, to form a wound body asillustrated in FIG. 2, and forming the conductive polymer layer betweenanode foil 21 and cathode foil 22. When the wound body is formed, thewinding may be performed while lead tabs 15A, 15B are rolled in theanode foil, the cathode foil, and the separator, to cause lead tabs 15A,15B to stand up from the wound body as illustrated in FIG. 2.

A material for lead tabs 15A, 15B is not particularly limited as long asthe material is a conductive material. Surfaces of lead tabs 15A, 15Bmay be subjected to an anodizing treatment. Further, lead tabs 15A, 15Bmay be covered with a resin material at a part in contact with sealingmember 12 and a part connected to lead wires 14A, 14B.

A material for lead wires 14A, 14B connected to lead tabs 15A, 15B,respectively, is not also particularly limited, and, for example, aconductive material may be used.

An end of an outer surface of anode foil 21, cathode foil 22 orseparator 23 that is positioned at an outermost layer of the wound body(cathode foil 22 in FIG. 2) is fixed with fastening tape 24. When anodefoil 21 is arranged by cutting a large metal foil, the capacitor elementin a state of, for example, the wound body, may further be subjected toan anodizing treatment in order to provide a dielectric layer on acutting surface of anode foil 21.

(Conductive Polymer Layer)

The conductive polymer layer is interposed between anode foil 21 andcathode foil 22. The conductive polymer layer is preferably formed on atleast a part of a surface of the dielectric layer formed on the surfaceof anode foil 21, so as to cover the dielectric layer. The conductivepolymer layer is more preferably formed so as to cover as large a regionof the dielectric layer as possible. The conductive polymer layer ispreferably formed on at least a part of a surface of the inorganicconductive layer formed on the surface of cathode foil 22, so as tocover the inorganic conductive layer. The conductive polymer layer ismore preferably formed so as to cover as large a region of the inorganicconductive layer as possible. When the capacitor element includes theseparator, the conductive polymer layer may be formed on not only thesurfaces of the dielectric layer and the inorganic conductive layer butalso a surface of the separator.

When the conductive polymer layer is formed with use of the dispersionobtained by dispersing fine particles of a conductive polymer in adispersion medium, a diameter of the fine particles of the conductivepolymer is preferred to be smaller than a diameter of the recesses onthe roughened surface of the cathode foil. The fine particles of theconductive polymer having such a diameter can attach also to a surfaceof recesses on the inorganic conductive layer to reduce the ESR of theelectrolytic capacitor.

(Conductive Polymer)

Examples of the conductive polymer included in the conductive polymerlayer include polypyrrole, polythiophene, polyfuran, polyaniline,polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, andpolythiophene vinylene. These conductive polymers may be used alone orin combination of two or more conductive polymers, or may be a copolymerof two or more monomers.

In the present specification, polypyrrole, polythiophene, polyfuran,polyaniline, and the like mean polymers having, as a basic skeleton,polypyrrole, polythiophene, polyfuran, polyaniline, and the like,respectively.

Therefore, polypyrrole, polythiophene, polyfuran, polyaniline, and thelike also include derivatives of polypyrrole, polythiophene, polyfuran,polyaniline, and the like, respectively. For example, polythiopheneincludes poly(3,4-ethylenedioxythiophene) and the like.

These conductive polymers may be used alone or in combination of two ormore conductive polymers.

A weight average molecular weight of the conductive polymer is notparticularly limited and ranges, for example, from 1,000 to 1,000,000,inclusive.

(Dopant)

The conductive polymer layer may include a dopant. The dopant may beincluded in the conductive polymer layer while doped in the conductivepolymer, or may be included in the conductive polymer layer while boundwith the conductive polymer.

As the dopant, a polyanion can be used. Specific examples of thepolyanion include polyanions such as polyvinylsulfonic acid,polystyrenesulfonic acid, polyallylsulfonic acid, polyacrylsulfonicacid, polymethacrylsulfonic acid,poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprenesulfonicacid, and polyacrylic acid. Especially, a polyanion derived frompolystyrenesulfonic acid is preferable. These polyanions may be usedalone or in combination of two or more polyanions. Further, thesepolyanions may be a polymer of a single monomer or a copolymer of two ormore monomers.

A weight average molecular weight of the polyanion is not particularlylimited and ranges, for example, from 1,000 to 1,000,000, inclusive. Theconductive polymer including such a polyanion is easily andhomogeneously dispersed in a solvent, facilitating uniform attachment ofthe conductive polymer to the surfaces of the dielectric layer and theinorganic conductive layer.

(Electrolyte Solution)

In a solid electrolytic capacitor, a high capacitance is expected byforming on a surface of a cathode foil an inorganic conductive layersuch as a carbon layer. With use of an electrolyte solution, however, itis difficult to suppress generation of an electrostatic capacity in acathode. Therefore, it has been conventionally considered that it isdifficult to actually achieve a high capacitance even with a combinationof the inorganic conductive layer and the electrolyte solution. In thepresent disclosure, however, it has been found that when the inorganicconductive layer is formed on the roughened surface of the cathode foiland the conductive polymer layer is formed with use of the dispersion orthe solution containing the conductive polymer, a decrease in adhesionbetween the conductive polymer layer and the inorganic conductive layercan surprisingly be suppressed to allow securement of a high capacitanceand reduce the ESR, even with use of the electrolyte solution. Further,the electrolytic capacitor including the electrolyte solution canfurther improve a function of restoring the dielectric layer.

As the electrolyte solution, a nonaqueous solvent may be used, or asolution may also be used that contains a nonaqueous solvent and anionic substance (solute) dissolved in the nonaqueous solvent. Thenonaqueous solvent is a collective term for liquids other than water andliquids containing water, and includes an organic solvent and an ionicliquid.

Examples of the nonaqueous solvent include a polyol (e.g., alkyleneglycols such as ethylene glycol and propylene glycol; polyalkyleneglycols such as polyethylene glycol; and glycerins such as glycerin andpolyglycerin), cyclic sulfones such as sulfolane, lactones such asγ-butyrolactone (γBL), amides such as N-methylacetamide,N,N-dimethylformamide, and N-methyl-2-pyrrolidone, esters such as methylacetate, ethers such as 1,4-dioxane, ketones such as methyl ethylketone, and formaldehyde. A single one or two or more in combination ofthe nonaqueous solvents may be used.

The electrolyte solution preferably contains at least a solvent (firstsolvent) having no boiling point or having a high boiling point (e.g.,180° C. or more) among the nonaqueous solvents described above. Theelectrolyte solution containing the first solvent can suppress depletionof the electrolyte solution even when the electrolytic capacitor is usedfor a long period, so that it is possible to secure high reliabilityover a long period. The electrolyte solution containing the firstsolvent, however, is likely to impair the adhesion between theconductive polymer layer and the inorganic conductive layer byinfiltrating between the layers through repetition of charging anddischarging.

Particularly, when a non-roughened cathode foil is used, the use of theelectrolyte solution containing the first solvent decreases the adhesionbetween the conductive polymer layer and the inorganic conductive layerto decrease the conductivity, so that it is impossible to secure acapacitance and reduce the ESR. In the present disclosure, the inorganicconductive layer is formed on the roughened surface of the cathode foil,so that it is possible to secure high adhesion between the conductivepolymer layer and the inorganic conductive layer even when theelectrolyte solution contains the first solvent.

The boiling point of the first solvent should be 180° C. or more and maybe 200° C. or more. As the first solvent, a polyol is preferable. Forexample, polyethylene glycol and polyglycerin sometimes do not have aboiling point depending on molecular weights of polyethylene glycol andpolyglycerin. Such a compound (limited to a liquid, however) is alsopreferable as the first solvent.

In the meantime, the first solvent is not necessarily contained in theelectrolyte solution used to assemble the electrolytic capacitor, butthe first solvent may be contained in a treatment solution used in aprocess of assembling the electrolytic capacitor. For example, thedispersion or the solution containing the conductive polymer may containthe first solvent. From the viewpoint of easily securing the adhesionbetween the conductive polymer layer and the cathode foil, a proportionof the first solvent contained in the dispersion or the solution ispreferably 50% by mass or less in the dispersion or the solution. Thefirst solvent having no boiling point or having a high boiling pointremains in the electrolytic capacitor assembled. The first solvent thathas remained oozes into the electrolyte solution housed in theelectrolytic capacitor, so that the electrolyte solution in theelectrolytic capacitor comes to contain the first solvent.

The proportion of the first solvent contained in the electrolytesolution ranges, for example, from 3% by mass to 90% by mass, inclusive,preferably from 10% by mass to 80% by mass, inclusive. The proportion ofthe first solvent contained in the electrolyte solution may also be setto a range from 10% by mass to 30% by mass, inclusive. The electrolytesolution having a proportion of the first solvent in such ranges cansuppress a decrease in adhesion between the conductive polymer layer andthe inorganic conductive layer and increase the function of restoringthe dielectric layer.

As the solute contained in the electrolyte solution, there can beexemplified a salt of an anion and a cation, and an organic salt ispreferable, in which at least one of the anion and the cation is anorganic substance. Examples of the organic salt include trimethylaminemaleate, triethylamine borodisalicylate, ethyldimethylamine phthalate,mono 1,2,3,4-tetramethylimidazolinium phthalate, and mono1,3-dimethyl-2-ethylimidazolinium phthalate. A single one or two or morein combination of the solutes may be used.

<<Method for Producing Electrolytic Capacitor>>

Hereinafter, one example of a method for producing the electrolyticcapacitor according to the exemplary embodiment of the presentdisclosure is described according to each of steps.

The electrolytic capacitor can be obtained through the steps of:preparing a dispersion or a solution (first treatment solution)containing a conductive polymer (first step); arranging an anode foil onwhich a dielectric layer is formed (second step); arranging a cathodefoil on which an inorganic conductive layer is formed (third step);obtaining a capacitor element by impregnating with the first treatmentsolution the anode foil, the cathode foil, and a separator interposedbetween the anode foil and the cathode foil, as necessary (fourth step);and impregnating the capacitor element with an electrolyte solution(fifth step). A conductive polymer layer can be formed through thefourth step. A solvent component may be removed in an appropriate stage.

(i) First Step

In the first step, a first treatment solution is prepared that containsa conductive polymer (and a dopant) and a solvent (second solvent).

The first treatment solution can be obtained by, for example, dispersingor dissolving the conductive polymer (and the dopant) in the secondsolvent. Alternatively, the first treatment solution can also beobtained by, for example, polymerizing in the second solvent a rawmaterial of the conductive polymer (e.g., a precursor such as a monomerand/or an oligomer of the conductive polymer) in presence of the dopant.In the case of preparing the first treatment solution throughpolymerization, an unreacted raw material and a byproduct may be removedas necessary. Alternatively, polymerization may be performed with use ofa part of the second solvent to give a mixture to which the remainingpart of the second solvent may be added.

The second solvent is not particularly limited, and may be water or anonaqueous solvent (e.g., an organic solvent and an ionic liquid).Especially, the second solvent is preferably a polar solvent. The polarsolvent may be a protic solvent or an aprotic solvent.

Examples of the protic solvent include a monohydric alcohol (e.g.,methanol, ethanol, propanol, and butanol); a polyol (e.g., alkyleneglycols such as ethylene glycol and propylene glycol, polyalkyleneglycols such as polyethylene glycol, and glycerins such as glycerin andpolyglycerin); glycol monoethers such as diethylene glycol monobutylether; formaldehyde; and water.

Examples of the aprotic solvent include amides such asN-methylacetamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone;esters such as methyl acetate; ketones such as methyl ethyl ketone andγ-butyrolactone; ethers (cyclic ethers) such as 1,4-dioxane; sulfonessuch as dimethyl sulfoxide and sulfolane; and carbonate compounds (e.g.,cyclic carbonates) such as propylene carbonate.

Especially, the second solvent is preferably a protic solvent. From theviewpoint of increasing handleability of the first treatment solutionand dispersibility of the conductive polymer, the second solventpreferably contains water. The second solvent containing a polyol islikely to increase the conductivity of the conductive polymer layer (inother words, likely to further decrease the ESR). Accordingly, thesecond solvent containing a polyol is also preferable, and use of thesecond solvent is also preferable that contains at least water and apolyol.

The first treatment solution is preferably a dispersion obtained bydispersing the conductive polymer (and the dopant) in the secondsolvent. In the dispersion, the conductive polymer and/or the dopant ispreferred to be particles (or a powder). An average particle size of theparticles dispersed in the dispersion preferably ranges from 5 nm to 100nm, inclusive. The average particle size can be determined, for example,from a particle size distribution obtained by a dynamic light scatteringmethod.

A ratio of the dopant contained in the first treatment solutionpreferably ranges from 10 parts by mass to 1,000 parts by mass,inclusive, more preferably from 50 parts by mass to 200 parts by mass,inclusive, relative to 100 parts by mass of the conductive polymer.

A concentration of the conductive polymer (including the dopant or apolyanion) in the first treatment solution preferably ranges from 0.5%by mass to 3% by mass, inclusive. The first treatment solution havingsuch a concentration of the conductive polymer is suitable forattachment of an appropriate amount of the conductive polymer and iseasily impregnated to also give advantages for productivity improvement.

The first treatment solution may contain, for example, a publicly knownadditive as necessary.

(ii) Second Step

In the second step, a surface of an anode foil is subjected to, forexample, an anodizing treatment to form a dielectric layer on thesurface of the anode foil, as described above.

(iii) Third Step

In the third step, a cathode foil is arranged on a surface of which aninorganic conductive layer is formed.

The inorganic conductive layer can be formed by a method such asattaching a powder conductive inorganic material to the surface of thecathode foil or vacuum vapor deposition. Alternatively, the inorganicconductive layer may also be formed by forming a coated film by coatingthe surface of the cathode foil with a paste or a slurry containing aconductive inorganic material and a binder, and drying the coated filmor removing the binder by subjecting the coated film to a heattreatment.

The inorganic conductive layer including a deposited film of aconductive inorganic material (particularly, conductive carbon such asamorphous carbon) can be formed by depositing, for example, theinorganic material on the surface of the cathode foil by a gas phasemethod such as chemical vapor deposition, vacuum vapor deposition,sputtering, or ion plating. For example, the inorganic conductive layerincluding a metal nitride may be formed by performing the gas phasemethod in a nitrogen gas atmosphere.

In the third step, the inorganic conductive layer may be formed byforming a base layer on the surface of the cathode foil as necessary andforming, as described above, a layer including the conductive inorganicmaterial on the base layer. The base layer constituting the inorganicconductive layer can be formed, in the same manner as described above,with use of the conductive inorganic material such as a metal or aconductive compound. The base layer is preferred to be formed bydepositing the conductive inorganic material on the surface of thecathode foil by the gas phase method.

(iv) Fourth Step

In the fourth step, the first treatment solution is impregnated into theanode foil on which the dielectric layer is formed, the cathode foil onwhich the inorganic conductive layer is formed, and a separator asnecessary. More specifically, in the fourth step, the first treatmentsolution may be impregnated into a wound body obtained by winding theanode foil on which the dielectric layer is formed and the cathode foilon which the inorganic conductive layer is formed, with the separatorinterposed between the anode foil and the cathode foil. The impregnationwith the first treatment solution may be performed by immersing thewound body in the first treatment solution or injecting the firsttreatment solution into the wound body. In the meantime, the inorganicconductive layer can be formed by roughening a surface of the cathodefoil and depositing an inorganic material having conductivity on theroughened surface of the cathode foil by the gas phase method.

The impregnation with the first treatment solution may be performedunder atmospheric pressure, but may also be performed under a reducedpressure, in an atmosphere ranging, for example, from 10 kPa to 100 kPa,inclusive, preferably from 40 kPa to 100 kPa, inclusive. Theimpregnation may also be performed under ultrasonic vibration asnecessary. An impregnation period depends on a size of capacitor element10, and ranges, for example, from 1 second to 5 hours, inclusive,preferably from 1 minute to 30 minutes, inclusive.

The anode foil and the cathode foil (and further the separator) may bedried as necessary after impregnated with the first treatment solution.The drying removes at least a part of the second solvent. The drying maybe performed by heating, and may also be performed under a reducedpressure as necessary.

As described above, the conductive polymer layer is formed between theanode foil and the cathode foil through the fourth step to thus formcapacitor element 10.

(v) Fifth Step

In the fifth step, the capacitor element obtained in the fourth step isimpregnated with an electrolyte solution.

The impregnation of capacitor element 10 with the electrolyte solutionis not particularly limited and can be performed by a publicly knownmethod. For example, capacitor element 10 may be immersed in theelectrolyte solution, or the electrolyte solution may be injected into acontainer housing capacitor element 10. The impregnation of capacitorelement 10 with the electrolyte solution may be performed under areduced pressure (e.g., 10 kPa to 100 kPa) as necessary.

(Others)

Capacitor element 10 may be encapsulated. More specifically, first,capacitor element 10 is housed in bottomed case 11 so that lead wires14A, 14B are positioned on an open upper surface of bottomed case 11. Asa material for bottomed case 11, there can be used metals such asaluminum, stainless steel, copper, iron and brass, or alloys of thesemetals.

Next, sealing member 12 formed so as to allow lead wires 14A, 14B topenetrate the sealing member is disposed above capacitor element 10 toencapsulate capacitor element 10 in bottomed case 11. Sealing member 12is sufficient as long as the sealing member is an insulating substance.As the insulating substance, an elastic body is preferable, andespecially preferred is, for example, a high heat resistance siliconerubber, fluororubber, ethylene propylene rubber, chlorosulfonatedpolyethylene rubber (e.g., Hypalon rubber), butyl rubber or isoprenerubber.

Next, bottomed case 11 is, at a part near an opening end, processed bytransverse drawing, and is, at the opening end, curled to swage sealingmember 12. Then, base plate 13 is disposed on a curled part of thebottomed case to complete the electrolytic capacitor as illustrated inFIG. 1. Then, an aging treatment may be performed while a rated voltageis applied.

In the exemplary embodiments described above, a wound electrolyticcapacitor has been described. The application range of the presentdisclosure, however, is not limited to the wound electrolytic capacitorand can also be applied to other electrolytic capacitors such as a chipelectrolytic capacitor including a metal sintered body in place of theanode foil, and a laminated electrolytic capacitor including a metalplate in place of the anode foil.

EXAMPLES

Hereinafter, the present disclosure is specifically described withreference to examples and comparative examples. The present disclosure,however, is not limited to the examples below.

Example 1

A wound electrolytic capacitor having a rated voltage of 35 V and arated electrostatic capacity of 47 μF, as illustrated in FIG. 1, wasmanufactured in the following procedure, and evaluation for theelectrolytic capacitor was conducted.

(1) Production of Electrolytic Capacitor

(Preparation of Anode Foil Having Dielectric Layer)

A 100-μm-thick aluminum foil was subjected to an etching treatment toroughen a surface of the aluminum foil. Then, a dielectric layer wasformed on the surface of the aluminum foil by an anodizing treatmentwith an ammonium adipate aqueous solution to arrange an anode foilhaving the dielectric layer.

(Preparation of Cathode Foil Having Inorganic Conductive Layer)

A cathode foil was arranged on a surface of which an inorganicconductive layer was formed. As the cathode foil, an aluminum foil(thickness: 30 μm) was used whose surface was roughened by an etchingtreatment and which had a surface expansion rate of 30 cm²/cm². Theinorganic conductive layer was formed on the surface of the cathode foilby ion plating of conductive carbon. A thickness of the inorganicconductive layer was 8 nm.

(Manufacturing of Wound Body)

An anode lead tab and a cathode lead tab were connected to the anodefoil and the cathode foil, respectively, and the anode foil and thecathode foil were would with a separator interposed between the anodefoil and the cathode foil while the lead tabs were rolled in the anodefoil, the cathode foil and the separator, to give a wound body. Ends ofthe lead tabs protruding from the wound body were connected to an anodelead wire and a cathode lead wire, respectively. Then, the manufacturedwound body was subjected to an anodizing treatment again to form adielectric layer at a cutting end of the anode foil. Next, an end of anouter surface of the wound body was fixed with a fastening tape.

(Preparation of First Treatment Solution)

A mixed solution was prepared by dissolving 3,4-ethylenedioxythiopheneand a dopant, i.e., polystyrenesulfonic acid in ion-exchanged water.Ferric sulfate and sodium persulfate (an oxidant) dissolved inion-exchanged water were added to the resultant solution while thesolution was stirred, to cause a polymerization reaction. After thereaction, a resultant reaction solution was dialyzed to remove unreactedmonomers and an excessive oxidant, so that a dispersion liquid wasobtained that included poly(3,4-ethylene dioxythiophene) doped withpolystyrenesulfonic acid (PEDOT-PSS). A concentration of PEDOT-PSS inthe dispersion liquid was about 2% by mass, and a mass ratio between PSSand PEDOT (=PSS:PEDOT) was about 2:1. Ethylene glycol (second solvent)at 5% by mass was added to the resultant dispersion liquid and stirredto prepare a first treatment solution having a state of a dispersionliquid.

(Impregnation with First Treatment Solution)

The wound body was impregnated with the first treatment solution for 5minutes. Next, the wound body was heated at 150° C. for 20 minutes toremove a solvent component. Thus, a capacitor element was manufacturedin which a conductive polymer layer was formed between the anode foiland the cathode foil.

(Impregnation with Electrolyte Solution)

Next, the capacitor element was impregnated with an electrolyte solutionunder a reduced pressure. Used as the electrolyte solution was asolution containing γBL, glycerin, and mono(ethyldimethylamine)phthalate (solute) at a mass ratio of 50:25:25. In the electrolytesolution, γBL and glycerin are a first solvent.

(Encapsulation of Capacitor Element)

The electrolyte solution-impregnated capacitor element was housed in anouter case as illustrated in FIG. 1 and encapsulated to manufacture anelectrolytic capacitor. A total of 300 electrolytic capacitors weremanufactured in the same manner.

(2) Evaluation of Performance

(a) Electrostatic Capacity and ESR Value

An electrostatic capacity (μF) and an ESR value (mΩ) were measured asinitial characteristics of the electrolytic capacitor. Specifically, aninitial electrostatic capacity (μF) at a frequency of 120 Hz wasmeasured for the electrolytic capacitor with an LCR meter for 4-terminalmeasurement. In addition, an ESR value (mΩ) at a frequency of 100 kHzwas measured for the electrolytic capacitor with an LCR meter for4-terminal measurement.

Also measured in the same manner as in the initial characteristicsdescribed above were an electrostatic capacity (μF) and an ESR value(mΩ) after a test of leaving the electrolytic capacitor to stand at ahigh temperature of 125° C. for 4000 hours.

The electrostatic capacities and the ESR values were measured for eachrandomly selected 120 electrolytic capacitors, and average values forthe electrostatic capacities and the ESR values were calculated.

(b) Proportion of First Solvent in Electrolyte Solution

The electrolyte solution was extracted from the electrolytic capacitor,and a proportion (% by mass) of the first solvent contained in theelectrolyte solution was measured by gas chromatography. The measurementresult indicated that the proportion of the first solvent in theelectrolyte solution was 76% by mass.

Comparative Example 1

An electrolytic capacitor was manufactured in the same manner as inExample 1 except for using as the cathode foil a non-roughened aluminumfoil (thickness: 20 μm), and the evaluation of performance wasconducted. The aluminum foil used had a surface expansion rate of 1cm²/cm².

Example 2

An electrolytic capacitor was manufactured in the same manner as inExample 1 except for using as the cathode foil an aluminum foil(thickness: 30 μm) whose surface was roughened by an etching treatmentand had a surface expansion rate of 1.5 cm²/cm², and the evaluation ofperformance was conducted.

Example 3

An electrolytic capacitor was manufactured in the same manner as inExample 1 except for using as the cathode foil an aluminum foil(thickness: 20 μm) whose surface was roughened by an etching treatmentand had a surface expansion rate of 2 cm²/cm², and the evaluation ofperformance was conducted.

Example 4

An electrolytic capacitor was manufactured in the same manner as inExample 1 except for using as the cathode foil an aluminum foil(thickness: 20 μm) whose surface was roughened by an etching treatmentand had a surface expansion rate of 10 cm²/cm², and the evaluation ofperformance was conducted.

Example 5

An electrolytic capacitor was manufactured in the same manner as inExample 1 except for using as the cathode foil an aluminum foil(thickness: 40 μm) whose surface was roughened by an etching treatmentand had a surface expansion rate of 60 cm²/cm², and the evaluation ofperformance was conducted.

Example 6

An electrolytic capacitor was manufactured in the same manner as inExample 1 except for using as the cathode foil an aluminum foil(thickness: 50 μm) whose surface was roughened by an etching treatmentand had a surface expansion rate of 80 cm²/cm², and the evaluation ofperformance was conducted.

Example 7

An electrolytic capacitor was manufactured in the same manner as inExample 1 except for using as the cathode foil an aluminum foil(thickness: 70 μm) whose surface was roughened by an etching treatmentand had a surface expansion rate of 120 cm²/cm², and the evaluation ofperformance was conducted.

Example 8

An electrolytic capacitor was manufactured in the same manner as inExample 1 except for using as the cathode foil an aluminum foil(thickness: 130 nm) whose surface was roughened by an etching treatmentand had a surface expansion rate of 500 cm²/cm², and the evaluation ofperformance was conducted.

Example 9

An electrolytic capacitor was manufactured in the same manner as inExample 1 except for forming an inorganic conductive layer (thickness 10nm) on the surface of the cathode foil by vacuum vapor deposition ofnickel, and the evaluation of performance was conducted.

Example 10

An electrolytic capacitor was manufactured in the same manner as inExample 1 except for forming an inorganic conductive layer (thickness 10nm) made from a titanium nitride on the surface of the cathode foil byvacuum vapor deposition, and the evaluation of performance wasconducted.

Comparative Example 2

An electrolytic capacitor was manufactured in the same manner as inExample 5 except for using the same cathode foil as the cathode foil inExample 5 without forming an inorganic conductive layer on the cathodefoil, and the evaluation of performance was conducted.

Comparative Example 3

A solution was prepared by mixing 1 part by mass of3,4-ethylenedioxythiophene as a polymerizable monomer, 2 parts by massof ferric p-toluenesulfonate that served as an oxidant and a dopantcomponent, and 4 parts by mass of n-butanol as a solvent. A wound bodymanufactured in the same manner as in Example 1 was immersed in theresultant solution, picked up from the solution and left to stand at 85°C. for 60 minutes to manufacture a capacitor element in which theconductive polymer layer was formed between the anode foil and thecathode foil. An electrolytic capacitor was manufactured in the samemanner as in Example 1 except for using the resultant capacitor element,and the evaluation of performance was conducted. The proportion of thefirst solvent in the electrolyte solution of the electrolytic capacitorwas 75% by mass.

Comparative Example 4

In Comparative Example 4, a solid electrolytic capacitor wasmanufactured that did not include an electrolyte solution. In the samemanner as in Example 1, a capacitor element was manufactured in whichthe conductive polymer layer was formed between the anode foil and thecathode foil. The resultant capacitor element was housed in an outercase and encapsulated to give a solid electrolytic capacitor, and theevaluation of performance was conducted in the same manner as in Example1.

Table 1 shows results of the examples and the comparative examples. A1to A10 denote Examples 1 to 10, and B1 to B4 denote Comparative Examples1 to 4.

TABLE 1 Electrostatic capacity (μF) ESR (mΩ) Initial After 4000 hoursInitial After 4000 hours B1 54.5 41.0 100.0 210.0 A2 55.0 46.0 69.0120.0 A3 55.0 48.0 68.0 105.0 A4 55.5 49.5 63.0 98.0 A1 55.5 49.5 63.098.0 A5 55.5 49.5 63.0 98.5 A6 55.0 48.5 66.0 102.0 A7 55.0 48.5 67.0106.0 A8 54.0 46.0 68.0 115.0 A9 55.0 48.5 69.0 102.5 A10 55.0 49.0 69.5105.0 B2 47.0 37.0 63.0 96.0 B3 55.5 40.0 70.0 155.0 B4 55.0 37.0 70.0120.5

In the examples, the initial electrostatic capacity was high and theinitial ESR was suppressed low as shown in Table 1. In ComparativeExample 1 where the non-roughened cathode foil was used, the initialelectrostatic capacity was high but the ESR increased. In ComparativeExample 2 where an inorganic conductive layer was not formed, theelectrostatic capacity decreased. In Comparative Example 3 where theconductive polymer layer was formed by polymerization, the ESRincreased.

In the examples, a relatively high electrostatic capacity could besecured and an increase in ESR was suppressed, even after theelectrolytic capacitor was left to stand at the high temperature for4000 hours. In contrast, after the electrolytic capacitor was left tostand at the high temperature for 4000 hours, the electrostatic capacitydecreased and the ESR remarkably increased in Comparative Examples 1 and3, and the electrostatic capacity largely decreased in ComparativeExample 2.

Comparative Example 4 had a larger value of an increase in a leakagecurrent value, which is not shown in Table 1, after the electrolyticcapacitor was left to stand at the high temperature for 4000 hours, thanExamples 1 to 10 and Comparative Example 1 to 4 had.

The present disclosure can be utilized for an electrolytic capacitorincluding a conductive polymer layer and an electrolyte solution.

What is claimed is:
 1. An electrolytic capacitor comprising: a capacitorelement; and an electrolyte solution, the capacitor element including:an anode foil provided with a dielectric layer on the anode foil; acathode foil disposed to face the anode foil and provided with a firstlayer on the cathode foil, the first layer including at least oneselected from the group consisting of carbon, nickel, a nickel compound,titanium, and a titanium compound; and a conductive polymer layerdisposed between the anode foil and the cathode foil, the conductivepolymer layer including a conductive polymer in contact with at least apart of a surface of the first layer, wherein the surface of the firstlayer has projections and recesses.
 2. The electrolytic capacitoraccording to claim 1, wherein the projections form a region where thefirst layer is in contact with the conductive polymer and the recessesform a region where the first layer is not in contact with theconductive polymer.
 3. The electrolytic capacitor according to claim 1,wherein the first layer includes a base layer disposed on the cathodefoil.
 4. The electrolytic capacitor according to claim 1, wherein thefirst layer includes at least one selected from the group consisting oftitanium, and a titanium compound.
 5. The electrolytic capacitoraccording to claim 1, wherein: the cathode foil has a roughened surfaceand the roughened surface of the cathode foil has a surface expansionrate ranging from 1.5 cm²/cm² to 500 cm²/cm², inclusive.
 6. Theelectrolytic capacitor according to claim 5, wherein the roughenedsurface of the cathode foil is provided by etching.
 7. The electrolyticcapacitor according to claim 1, wherein the electrolyte solutioncontains a first solvent having no boiling point or a boiling point of180° C. or more.
 8. The electrolytic capacitor according to claim 7,wherein the first solvent contains a polyol.
 9. The electrolyticcapacitor according to claim 7, wherein a proportion of the firstsolvent contained in the electrolyte solution is ranging from 3% by massto 90% by mass, inclusive.